A connector housing for an automobile is injection-molded of a resin. Polyamides such as nylon, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and polycarbonates are used in the molding. Among these, polybutylene terephthalate (hereinafter, abbreviated to PBT) is often used since PBT has excellent mechanical properties, electrical properties, heat resistance, water resistance, and the like. Moreover, PBT is a crystalline resin, and leads to high productivity by achieving a fast crystallization rate, and solidification in a short time. Due to these advantages, PBT is frequently used as a molding material of a connector housing for an automobile.
Along with reduction in size of wire harnesses and the like, there has been a demand for reduction in size and thickness of the connector housings. In conventional practice using PBT as the molding material of the connector housing, fibers such as glass fibers are added to the PBT to meet such demand and also to increase the strength of the connector housing. Patent Literature 1 describes a conventional technique of adding fibers, in which glass fibers having flat cross sections and glycerol esters of fatty acids are mixed into PBT.